SPF, which is short for Sender Policy Framework, is an e-mail security system, which is is intended to verify if an e-mail message was sent by a certified server. Employing SPF protection for a domain name will stop the forging of emails created with the domain. In simple words: activating this function for a domain name creates a specific record in the Domain Name System (DNS) that contains the IP of the servers that are allowed to send email messages from mailboxes under the domain. When this record propagates worldwide, it will exist on all the DNS servers that route the Internet traffic. Every time an e-mail message is sent, the first DNS server it uses tests whether it originates from an official server. In the event it does, it's forwarded to the destination address, however when it does not come from a server listed in the SPF record for the particular domain, it's discarded. Thus nobody will be able to mask an email address then make it look as if you are sending spam messages. This technique is also known as email spoofing.